Processes, feedbacks, and morphodynamic evolution of tidal flat–marsh systems: Progress and challenges

Tidal flats and saltmarshes have been a long-standing research focus because of their high socio-economic and ecological values. The evolution of tidal flat–marsh systems is highly complex due to the intertwined processes operating over a variety of spatial and temporal scales. As a traditional research highlight, the role of regular hydrodynamic processes such as tides, waves, and river flows have been explored comprehensively with fruitful outcomes. Over past decades, the changing environment (e.g., sea level rise, increasing anthropogenic activities, and extreme weather conditions) has attracted more attention with many reported insightful results. More recent advances indicate that biological activities play a critical role in tidal flat–marsh morphodynamics but are still poorly understood. The field of research that connects the biological and physical processes is commonly described as “biogeomorphology” and requires the joint efforts by scientists from multiple disciplines ranging from hydraulics, ecology, and geography to sociology. This review aims to provide a synthesis of the current research status of tidal flat–marsh morphodynamics, with a particular emphasis on the understanding of various processes and feedbacks underlying the development of morphodynamic models. Some future research needs and challenges are identified to facilitate a more sustainable management strategy for tidal flats and saltmarshes under climate change.